Fable is an earnest but uneven effort. Its eye-grabbing graphics and decent voice acting do not make up for its minimally challenging and unoriginal puzzles, abundant anachronistic humor, and design flaws.
Fable falls into the King's Quest vein of point-and-click, inventory-oriented graphic adventures. But it fails to meet the high quality we've come to expect from the best of that genre.
I'd set up the back story for you but it's too convoluted and confusing. The quest is easier to explain. Basically, you're in a fictional medieval kingdom. A priest volunteers you, for no apparent reason, to visit four magical lands, slay their four beastly rulers, and recover four jewels. Success will somehow bring peace and tranquility to your hometown.
Fable's adventure elements - look everywhere, pick up everything, insert object here, use combination there - are generally routine. There are a few problems and some obscure hidden hot-spots, but most experienced adventurers will find nothing new or overly ambitious here.
The inventory gathering sometimes defies logic. Feel free to rummage through a witch's pantry and cellar while she sleeps, blithely unaware of your kleptomania. There's no need to trick her or interact with her in any way. She's just a prop, as are several other characters. Slaying the bad guys is fairly straightforward, and they generally give you ample time to find the right item to accomplish your task.
There are some nagging design problems: The settings, while superbly colored and detailed, are diminished by the herky-jerky animation and non-lip-synched dialogues. When you die, nothing happens. The first few times you have no idea whether or not you're still playing the game. You need to hit escape to finally bring up a menu and restore a saved game. And the interface is clumsy. Instead of having the most logical action be the first to appear, you usually have to click through a whole smorgasbord of selections before finding what you need.
In what appears to be a medieval setting, the bathroom and juvenile jokes are jarring and misplaced and the characters speak with a multitude of modernisms - complete with contemporary slang. These issues wouldn't be such a problem if Fable had any sense of identity, but the game switches between fantasy and farce without warning.
Finally, the ending(s) are terrible. The UK version has two, neither very satisfying: You die in a cave-in or celebrate your twenty-first birthday in prison after having "merged your family with a frozen mackerel at the age of three," whatever that means. So Sirtech wanted to come up with what I guess would be considered a more satisfying ending for the US version. I won't tick them off further by telling you what it is - but I will say they failed miserably.
All that said and done, should you buy Fable? If you're a fan of graphic point-and-click adventures looking for a mildly entertaining, two-day diversion and you see Fable on the remainder rack, sure. Enjoy the eye-candy and problem solving, and perhaps a few yuks at the inappropriate jokes, but don't expect much else.